The three cubes represent three stages in a computer simulation of the formation of protogalactic clouds; they represent a region about 500 million light-years across. Which of the following statements about this model is true?
1. The gas in the third frame looks very dis-organized, but the model indicates that all this gas soon became the spiral arms of a large spiral galaxy.
2. Although the gas in the three frames looks fairly stationary, the model assumes that the entire blob of gas must have been rotating rapidly.
3. Although the model shows only visible gas, it assumes that there were supermassive black holes randomly distributed throughout the universe.
4. Although the gas looks uniform in the first frame, the model assumes there were small regions with slightly higher densities than other regions.